W205 radio stopped working

[shall10]

I have a W205 C250, 64-plate. About two years ago the radio suddenly stopped working, and an autoelectrician checked everything - fuses, wiring etc, out but couldn't find the fault. Everything else in Comand works fine - satnav, media etc, and I can still get traffic announcements but only from local radio stations. Then about a year ago I started the engine and the satnav had updated itself with different map design, and wiping all my data - favourites etc. And the radio started working! However, after a few months it died again, and only shows a few horizontal lines on screen when selected. I don't want to take it to my local MB dealer @ £160/hr, so looking for any advice to fix it.

Thanks